Darlot lens question

Hi all--
This is going to be a long shot, but what the hell. I just picked up a brass barrel lens of some sort. It is 3 1/2" tall and about a 2" diameter. There is only one visible marking on the barrel, a stamped "3". I'm not sure if there are missing pieces, elements, etc. but it doesn't really seem to do anything! When I took the elements out, I can see that they say Darlot Paris on the sides of the elements. At least that is how I decipher it. So based on that crappy description and the attached photos, does anyone have an idea what this lens is and/or what is missing? Thanks in advance.
Matt

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"Everytime I find a film or paper that I like, they discontinue it." -Paul Strand

I had a similar question a couple of years ago on here and learned a lot from other members. I have since picked up even more. The lens you have is one of a multiple used in cameras like this. They were common in photo studios producing carte de visite and gem photos in the second half of the nineteenth century. A tin type could be exposed with multiple views or at the same time (one view) and then cut up.

As you may be able to see from the camera referenced, the threaded end of the barrel was toward the sitter, not the film plane, as the lens board was a sheet of brass with threaded holes and the lens barrels projecting back toward the plate. I have found some of these lenses with the elements reversed by previous owners so that the threaded end could be screwed into a flange and the lens project out toward the sitter. This catalogue, from the very informative antiquecameras.net site, shows the Darlot Gem lenses. It also has a great little bit at the end of the Darlot section on the proper positioning of elements in Darlot lenses.

I'm not completely sure of the differences between series 3 and the other series made by Darlot. It is a reference to focal length and coverage, I believe, but I don't have the exact relationship clear in my head. The one I had was a 4 and covered about a 3 1/2 inch image circle. Here is an image shot with it on 4x5 film.

There should be 3 pieces of glass. The one in the 5th picture is the front cemented doublet and should 'point' towards your subject. From the photos, it looks like you are missing the third lens element, but maybe I'm mis-interpreting your photos. There should be a thick front doublet, a thinner rear piece, and an even thinner and more bowed piece, usually with a metal ring between the back two pieces. If there aren't 3, it either isn't a petzval (and it should be a Darlot gem from the look), or you don't have it all.